Abandon all spoilers, ye who enter here. Our analysis of Phil Resch's character is going to be chock-full of spoilers. This is because we really can't talk about him without revealing whether he is an android or a human. So, spoiler warnings are in full effect on this one starting…now.
Phil Resch is a fellow bounty hunter and briefly Rick's partner. They meet in the android-run police station where Resch is employed, and just about the first thing we see Resch do is shoot his superior officer Garland, right when Resch realizes that the guy's an android.
Nice to meet you too, Resch.
This shooting saves theirs butts (Garland is about to preemptively kill them) but not before Garland manages to suggest to Rick that Resch just might be an android with false memories. Resch eventually picks up on this doubt, and both of them start to question his humanity—and not just because he's a stone-cold killer.
Resch comes down on the human side. He claims he can't possibly be an android because he owns a squirrel—a real one. As he tells Rick, "I own an animal; not a false one but the real thing. A squirrel. I love the squirrel, Deckard" (11.52). The underlying argument is that an android couldn't possibly care for a squirrel because it only cares about itself.
But Deckard isn't convinced, especially after he guns down Luba Luft in cold blood. As he tells Resch, "I see a pattern. The way you killed Garland and then the way you killed Luba. You don't kill the way I do; you don't try to—Hell," [Rick] said. "I know what it is. You like to kill. All you need is a pretext" (12.62).
Eventually, both men's theories are put to the Voigt-Kampff test, and the results come back negative. Resch is a human through and through. But why does the novel play this game with us? Why not just come out and reveal Resch is a human from the start?
Oh, just for the little reason that Resch is Rick's foil, the character we're meant to compare and contrast with our protagonist. In fact, we're not the only ones making that comparison. Rick does it himself, recognizing in Resch a part of himself that he doesn't like.
This comparison triggers a major change for Rick. After the Voigt-Kampff test, Rick realizes that Resch's lack of empathy toward androids makes him a good bounty hunter—and a bad human (12.128). As he tells Iran after buying the goat:
"I met another bounty hunter," [Rick] said. "One I never saw before. A predatory one who seemed to like to destroy them. For the first time, after being with him, I looked at [the androids] differently. I mean, in my own way I had been viewing them as he did." (15.65)
This is a major contrast from Resch's reasoning for bounty hunting, which is that the Nexus-6 "would roll all over [humanity] and mash us flat." For Resch, bounty hunters are the only thing protecting mankind and keeping it and androids "distinct" (12.100). You have to police those boundaries, right? Don't want any of that ungodly miscegenation.
Basically, Resch is Rick's possible future. They even go through a lot of the same experiences, like both sleeping with Rachael. The difference? Resch managed to keep on retiring androids afterwards. In fact, he's the only guy who was ever able to be with Rachael and still go out and kill. But—"Going through this," Rick says, "I can't blame him. It warped him" (17.54).
Rick's conflict for the remainder of the novel is to prevent himself from transforming into a person as warped as Resch. Does Rick succeed or does he become Resch v2.0? You'll have to check out his Character Analysis to find out.